/Engine/Source/Runtime/OpenGLDrv/Public/OpenGLDrv.h
With RHI thread, this is the current backbuffer from the perspective of the render thread. FlushType: Thread safe
virtual FTexture2DRHIRef RHIGetViewportBackBuffer ( [FRHIViewport](API\Runtime\RHI\FRHIViewport) * Viewport )